Constructed of material that minimally attenuates an electromagnetic signal transmitted or received by an antenna, an aircraft radome provides a radiolucent (i.e. rf transparent) weatherproof aerodynamic fairing. Radomes often appear as dome-like blisters on the fuselage of aircraft. To minimize drag, such radomes typically have a low profile, providing extremely limited space for an antenna and its related equipment. A contained antenna may be used for air to ground, satellite or aircraft-to-aircraft communication.
Heretofore, antennae having parabolic reflectors have been avoided in such aircraft radome applications, due to space constraints. Such limited space makes it difficult to illuminate the entire reflector surface, when the aspect ratio of the reflector is high and the feed is positioned only a short distance away.
Forgoing antennae having parabolic reflectors, antenna arrays comprising an array of flat panels have been devised to fit within aircraft radomes. While such high aspect ratio antennas provide adequate gain to close a communication link, they experience low aperture efficiencies and high sidelobe levels and grating lobes in some locations. High sidelobes and grating lobes are undesirable features of the solutions, with sidelobes representing unwanted radiation in undesired directions becoming a potential cause of interference and reduced signal to noise ratio. A spatial aliasing effect may cause some sidelobes to become substantially larger in amplitude, and approaching the level of the main lobe. Such sidelobes are called grating lobes. The efficiency of these antennas can be lowered due to the losses of beamformer networks required to feed the array elements.
By way of example, in-flight broadband connectivity and wireless in-flight entertainment for commercial aircraft, including Southwest Airlines, is provided using a Ku-band antenna system, comprised of a flat panel array, mounted atop the aircraft fuselage and encased within an RF-transparent radome. Such antenna systems communicate with geostationary satellites, allowing uninterrupted in-flight Wi-Fi service over water and on airlines' routes virtually anywhere in the world. Low aperture efficiencies, high sidelobes, grating lobes and losses of beamformer networks, and heavy weights compromise performance of such antenna systems.
The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.